Tonight we're going to zip up our windbreakers and camp out in our folding chairs, drinking coffee from a thermos, until the ghostly Marfa Lights make their appearance, hovering and wavering out in the field before us.

In 1957, a magazine article first reported the mysterious phenomenon of hovering balls of light bouncing around the night near Marfa, Texas. About ten miles east of Marfa, in an area called Mitchell Flat, the odd lights appear perhaps a couple dozen times per year. They're about the size of basketballs and appear to float about shoulder high. Sometimes several appear at once, wavering about, sometimes even merging together or moving about in a group, splitting apart, and behaving in a most remarkable fashion. They only appear at night, at any time of year and in any weather, and are usually white or yellow or orange. Sometimes red or blue are reported, but most are white.

One unique characteristic of the Marfa Lights is that they are actually there and can actually be observed; their existence is definitely not just a story. The city of Marfa has even erected a viewing platform, where hopeful light spotters can be found every night. You can actually go there, and if you're lucky or patient enough, you will actually see the Marfa Lights.

The default skeptical explanation which is readily put forth is that the Marfa Lights are simply car headlights, seen from a great distance and distorted by temperature gradients. Critics of this explanation quickly point out that the Marfa Lights have been reported for hundreds of years, since long before there were any car headlights around.

Well, apparently, the Marfa Lights have not been around all that long, after all. The earliest accounts come from a rancher named Robert Ellison in 1883. However, upon closer inspection, it appears that there is no actual record that Robert Ellison ever saw such a thing. There are reports from his descendants that Ellison said he saw lights, but there is no written record, not even when he wrote his memoirs about his life in the region in 1937. Curious that he would leave that out. Apparently, all evidence that the lights existed prior to the arrival of automobile highways in the region is purely anecdotal. Throughout history there have been hundreds and hundreds of reported "ghost lights" that probably never existed outside of the observers' whiskey-soaked imaginations. Those ghost lights that have become famous are those few that are observable today, such as the Marfa Lights, and almost all have multiple versions of illustrious histories invented for them. A similar phenomenon in Arkansas called the Gurdon Light is said to be the swinging lantern of a brakeman accidentally beheaded by a passing train. Not surprisingly, the exact same explanation is put forth for the Big Thicket Ghost Light in Bragg, Texas. These ghost lights can't all be headless brakemen, so it's conceivable that the folk explanation is not true in every case.

So what are these lights, you ask, and why can't someone run out there and track one down? There are two reasons why this is easier said than done. First, it's illegal. All the property in the area is privately owned, most of it by people who are tired of these tourists chasing around in the night, and do not welcome them. Second, the terrain is exceptionally difficult to traverse. However, hardy souls have made the attempt on numerous occasions. At least two television shows have done just this, and wisely staked out people in different locations in an effort to triangulate and precisely locate the lights. But, as luck would have it, these triangulation efforts have never been successful. The only thing conclusively demonstrated was that the lights are not where they appear to be. This has effectively put to bed other theories, such as the suggestion that piezoelectric effects from the quartz bedrock causes ball lightning. If ball lightning was floating around out there, searchers would be easily able to triangulate and close in on it.

Unfortunately for all of those like myself who love a good mystery, and contrary to what's printed in all the Marfa tourism brochures and on all the ghost light websites, the Marfa Lights have been thoroughly and definitively explained. The same explanation most likely applies to many similar lights around the world. If you prefer a mystery and don't want to hear it, then turn off your iPod now. It's a spoiler, and like all spoilers, it's disappointing.

May I have the envelope, please? The winner is ... the car headlights combined with some fascinating atmospheric phenomena. In 2004, The University of Texas sent the Society of Physics Students, a highly respected professional association, to investigate the Marfa Lights. Their official report, available online, found conclusively that when the lights appeared, they were precisely correlated with car headlights on Highway 67. The lights were completely predictable and the phenomenon was fully repeatable, based on cars on the highway. Quite a few photographs have been taken of the lights at night, which when superimposed upon a photograph from the same camera location during the day, show Highway 67 in the extreme distance, precisely in the same place as the light in the night photograph. The strange movement of the lights is attributed to the magnifying or shimmering effect caused by a superior mirage, in comparison to the more common inferior mirage. Superior mirages, where objects appear higher than their actual position, can make distant objects — even those below the horizon — appear to hover in the air. Inferior mirages, where objects appear below their actual position, can make objects up in the air, such as a patch of sky, appear below the horizon, like the proverbial lake in the desert. Anytime the temperature gradients are suitable, the Marfa Lights should appear and behave predictably. Other independent investigations have also found the same correlation with cars on nearby Highway 90.

Correction: An earlier version of this erroneously suggested some of the light effects could be caused by a Fata Morgana mirage, a type of complex superior mirage that is unlikely to occur in the Marfa environment. - BD

There are still critics who do not accept what the investigations have revealed, in some cases because of the stories of reports that predated the highways. These critics are reminded that there is no record of Marfa Lights reports before the appearance of automobiles in the area. And anyway, a lantern or other light would be affected in exactly the same way as the car headlights are today.

Some reports talk of the lights hovering above a person, moving around them, or behaving in other ways inconsistent with the SPS explanation. The Marfa Lights have been photographed and videotaped exhaustively, but none of that evidence supports such reports. Many such reports are probably hoaxes, imagination, or exaggerated recollections. However, it is very difficult to judge the distance of a light source distorted by an inversion layer. Many reports of people getting within a few meters of a Marfa Light are probably quite genuine: Every visible indication would be that the light appears to be hovering eerily just out of reach.

Considering the evidential consistency and comprehensiveness of the SPS investigation, and its numerous independent verifications, I see no reason to doubt that the mystery has been conclusively solved, and certainly see no need for bizarre and unprecedented alternative explanations like the piezoelectric lightning balls. I'm still a little worried about encountering a headless lantern-swinging brakeman in the dead of night, but that's only because I'm afraid he might want my head, Ichabod Crane style.